Within a 3GPP communication network, a Policy and Charging Rules Function (PCRF) supports the creation of rules and makes policy decisions for subscribers to the network. One of the functions of the PCRF is to make policy decisions for subscribers based on individual subscriber spending limits. An Online Charging System (OCS) maintains real-time policy counters for subscribers, and the status of these counters is used by the PCRF as input to policy decisions.
The Sy reference point is located between the PCRF and the OCS, and enables transfer of policy counter status information relating to subscriber spending from the OCS to the PCRF. The Sy reference point is illustrated in FIG. 1, which demonstrates relationships between different functional entities in a reference network architecture 100. The Sy reference point is specified in 3GPP Technical Specification 29.219 and supports the following functions:
Request from the PCRF to the OCS for policy counter status reporting.
Subscription/un-subscription by the PCRF to/from notifications from the OCS of policy counter status changes.
Notification of spending limit reports from the OCS to the PCRF.
When the status of policy counters is first required by the PCRF to make a policy decision for a network user, the PCRF uses an Initial Spending Limit Report Request procedure. The PCRF may request one or more specific policy counter statuses for the network user, or may request all policy counter statuses be reported by the OCS for the user. The OCS then provides the status to the PCRF of the requested policy counters, and will notify the PCRF of any changes in the status of those policy counters.
The PCRF may request reporting for a specific policy counter or counters to which it is not currently subscribed, and/or may cancel reporting for specific policy counter statuses using an Intermediate Spending Limit Report Request. The PCRF may cancel spending limit reporting for all policy counters for a user via a Final Spending Limit Report Request.
An Sy session between the PCRF and OCS is initiated when an Initial Spending Limit Report Request is issued by the PCRF for a user. The Sy session is terminated when a Final Spending Limit Report Request is issued by the PCRF for the user. Each spending limit report request is specific to a particular Sy session. Occasionally, circumstances may require a PCRF to add or remove subscription to one or more policy counters for multiple ongoing Sy sessions at the same time. This may be the case for example in the event of a promotional offer that applies to multiple customers. In such circumstances, the issuance of multiple Intermediate Spending Limit Report Requests, one for the Sy session of each subscriber affected by the offer, leads to a signalling burst between the PCRF and the OCS which may be detrimental to overall network performance.